This invention relates to a body support system such as may be used for a seat cushion. More particularly, this invention relates to a body support system such as may be used for a seat cushion and having improved mechanical response characteristics and improved thermal interaction with a user.
The comfort provided to a user by a body support system such as a seat cushion will depend on a variety of factors. One such factor is the mechanical response of the body support system to the compressive and shear forces applied by a user seated on the body support system. Another such factor is the ability of the body support system to provide thermal regulation in the form of heat exchange with a user. If the body support system is to be used in conjunction with a moving device such as a wheelchair, a farm implement such as a tractor or riding mower, or as a seating element for public transportation, then the ability of the body support system to provide dynamic response to reduce transmission of impact to a user is another factor.
Conventional contemporary office seats are usually made of either upholstered padding or synthetic mesh in a frame assembly. Each of these types of seats has its own characteristic thermal properties. Padded upholstery seating provides heat exchange with the user through conduction and sweat evaporation processes. Upholstered padding is better suited for lower workspace temperatures on the order of 16-25xc2x0 C. (61-77xc2x0 F.) and shorter sitting times. Mesh seating provides heat exchange with the user with radiation and convection. Mesh chairs are better suited for higher workspace temperatures on the order of 25-35xc2x0 C. (77-95xc2x0 F.) and longer sitting times. Neither of these prior art seating designs provides for thermal regulation in a wide variety of office temperature environments.
Thermal properties are major ergonomic features that should be considered in the design of an office chair. The human body always works to retain its core temperature near 37xc2x0 C. (98.6xc2x0 F.), by means such as postural adjustments, varying skin temperatures such as by perspiration, regulation of cardiovascular and pulminary activity such as pulse and breath rates to affect blood flow and vessel sizes especially in skin areas close to an interface with a seat cushion. A chair that prompts sweating after a relatively short period of sitting and which requires the human body to engage in such thermal regulation processes will be uncomfortable and may affect work efficiency. For example, with conventional upholstered padding, heat can build up at the user/seat interface causing the user to limit muscular activity to reduce heat generation. The user may also begin sweating to expedite the thermal transfer across the user/seat interface. When the user/seat interface inhibits sweat evaporation due to low cushion vapor permeability under even small pressures, heat is not dissipated at the interface leading to even greater discomfort for the user. On the other hand, mesh chairs have high vapor permeability and heat dissipation and do not allow for any heat build up at the seat user interface. It has been postulated that a limited heat build up that would not reach a level of discomfort to the user would be favorable. Thus, with open mesh seats the thermal comfort of the user becomes significantly dependent on the ambient temperature of the work environment.
Further, conventional seating designs do not provide for variations in the size and comfort levels of different users. Different individuals will have different thermal generation rates and different comfort levels.
It is thus one object of the invention to provide a body support system such as a seat cushion having improved thermal regulation properties.
It is yet another object of the invention to provide a body support system such as a seat cushion having improved mechanical response properties including low intensity pressure distribution.
It is still another object of the invention to provide a body support system such as a seat cushion in which the thermal regulation properties and/or the mechanical characteristics can be varied to the needs or preferences of a particular user or group of users.
A body support system is provided having improved static support characteristics and improved thermal interaction with a user. The improved static support is provided by means for distributing the weight of a user in response to applied compressive and shear forces at the user-support system interface. The means for distributing the weight of the user comprises a plurality of vertical columns disposed substantially centrally in said body support system. The columns are capable of deflecting substantially independently of one another in response to the compressive forces applied by a user. The improved thermal interaction is provided by structures that provide enhanced air flow through and about said body support system, thereby providing convective thermal regulation, and dry and evaporative heat exchange. An elastomeric member disposed above said columns also serves to facilitate heat exchange with a user, and cooperates with the columns in the distribution of the user""s weight for improved static support.
The body support system comprises a foam body. In one embodiment, the vertical columns can be configured as upwardly extending risers, formed integrally with said foam body. In an alternative embodiment, the columns can extend downwardly from the elastomeric member. The columns can be formed of a material having density and mechanical response characteristics either the same as or different from the density and mechanical response characteristics of the foam body. This feature permits the inventive body support system to be customized to the needs of different users.
The spaces between the vertical columns define an air reservoir within the interior of the body support system. The body support system further comprises means for directing the flow of air from the air reservoir to the periphery of the body support system, and then toward the upper surface thereof, for heat exchange processes with the user, thereby increasing the comfort of the user when using the body support system for long periods of time. The means for directing the flow of air from the air reservoir to the periphery can comprise a plurality of channels formed within the foam body and extending from the air reservoir to the foam body periphery. When compressive forces are applied by a user, air within the reservoir will be displaced and directed through the channels toward the periphery and upwards. Advantageously, air flow through the body support system is achieved without the need for active airflow circulation devices such as fans, valves, or pumping devices. Air deflecting means disposed about the periphery of the foam body function to deflect the air received at the periphery from the reservoir to a region above the foam body for heat exchange with the user. This thermal regulation function is further enhanced by the aforementioned elastomeric member, which functions as a large capacity heat sink to remove heat from the user.
The body support system of the instant invention can further comprise an air-permeable viscoelastic layer disposed above the elastomeric member and the foam body. The viscoelastic layer can reduce the transmission of both compressive and shear forces to the elastomeric member. The air-permeable viscoelastic layer can also facilitate the flow of displaced air at the periphery of the cushion to enhance thermal regulation. The airflow achieved with the body support system of the instant invention also contributes to mechanical function of the body support system by providing recoverable dissipation of applied shear and compressive forces
The body support system of the instant invention can be used in a wide variety of seating applications. The body support system can be configured as a seat cushion such as for use in office seating, in which case the seat cushion can be mounted onto a chair frame including a pre-formed seat pan. The seat pan acts as a rigid support for the cushion. The body support system can also be used in rehabilitative seating and other support, such as in wheelchairs, hospital beds, and the like, where improved responsiveness to compressive and shear forces can help in the prevention of decubitus ulcers. The inventive body support system can also be used in dynamic situations such as motor vehicles, particularly vehicles driven for long periods of time such as trucks, and even more particularly vehicles driven for long periods of time over uneven surfaces, such as snowplows and farm implements, which vehicles are subject to motion-induced vibration and in which the vehicle driver can benefit from the damping of such motion-induced vibration as can be provided by the inventive body support system disclosed herein.